Completed projects

Ballard Siphon replacement

King County built a new 85-inch siphon pipe under Salmon Bay between the Ballard and Interbay areas of Seattle to accommodate growth in north Seattle and reduce combined sewer overflows into Salmon Bay.

Barton CSO control / green stormwater infrastructure

King County constructed 91 roadside rain gardens, a type of green stormwater infrastructure, in the Sunrise Heights and Westwood neighborhoods of West Seattle. These roadside rain gardens divert stormwater runoff away from the combined sewer system to reduce CSOs of raw sewage and untreated stormwater into Puget Sound near the recently upgraded Barton Pump Station and Fauntleroy ferry dock.

Learn more by visiting the operations page for the Barton CSO control facility (roadside rain gardens).

Barton Street Pump Station upgrade

This project increased station pumping capacity from 22 million gallons per day (mgd) to 33 mgd, replaced outdated electrical equipment, pumps and associated equipment, and constructed a new underground valve room and installed new valves on the force.

Bellevue Pump Station upgrade & force main installation

This project was completed in two phases. During phase one (completed spring 2008), a new 5,300-foot-long, 24-inch-diameter pipeline was installed from the Bellevue Pump Station directly to the Eastside Interceptor, a large regional pipe near Interstate 405. During phase two, the 40-year old pump station was demolished and replaced with a facility featuring more powerful pumps, a new generator building, stronger odor control equipment and updated architecture.

Bellevue influent trunk improvement

King County and the City of Bellevue upgraded 45-year-old sewer trunk lines along SE Third Street and 102nd Avenue SE in Bellevue to provide the required capacity to accommodate recent and projected growth in Bellevue.

Brightwater Treatment System

In response to increased growth in our region, King County has built a new regional wastewater treatment system called Brightwater to serve the northern portion of the King County service area. Treatment plant operations began in September 2011. The conveyance system and outfall began full operations in fall 2012.

Denny Way/Lake Union CSO control

Providing additional storage and treatment that will greatly reduce the number of untreated combined sewer overflows from the Denny Way wastewater regulator station.

Denny Way Regulator Station upgrade

King County completed construction work at the Denny Way Regulator Station in Myrtle Edwards Park on Elliott Bay. The sampling equipment was updated and a sampling room added to the facility.

Eastgate Interceptor lining

King County has completed rehabilitating a 2,400 foot-long section of the twin Eastgate Interceptor lines. This project will extent the useful life of this pipeline another 50 years.

Eastside Interceptor Lining Project

This is part of the conveyance system program created to rehabilitate corroded conveyance pipelines throughout the county’s wastewater system. This project is located in Renton.

Eastside Interceptor (Section 13) Lining

This work is part of a program to restore corroded sewer lines throughout the regional wastewater system. Pipe lining is a cost-effective way of maintaining the sewer lines. It saves on materials and energy use, when compared to installing new sewer lines.

53rd Avenue Pump Station upgrade

This Alki area pump station improvement project features new odor control equipment, upgrades to the facility's electrical and mechanical systems, and doubling the size of the below-ground facilities.

Fremont siphon replacement

King County constructed a new pipeline beneath the Lake Washington Ship Canal to carry untreated wastewater from Seattle's Fremont neighborhood to the West Point Treatment Plant in Magnolia. The previous pipeline, in service for more than 100 years, has been decommissioned.

Henderson/M.L. King CSO control

This project is one of King County's largest combined sewer overflow control projects. Besides helping protect the water quality of Lake Washington, it provides many needed improvements to the Rainier Beach sewer system, much of which is more than 50 years old.

Hidden Lake pump station replacement and sewer improvement

The county replaced its existing 40-year-old Hidden Lake Pump Station with a new 6.8-million-gallon-a-day pump station and 12,000 feet of new sewer trunk line near Boeing Creek in Shoreline. The project increased system reliability by adding capacity that will help reduce overflows into Puget Sound during heavy rains. Other investments include a 500,000-gallon-capacity underground wastewater storage pipe in Boeing Creek Park and an upgraded a City of Shoreline stormwater detention pond.

Interbay pump station

This project increased station pumping capacity, replaced aging equipment, and constructed a new generator building to provide emergency power and improve the pump station’s reliability.

Juanita Bay pump station replacement

This pump station replaced an older station and increases sewer system capacity while providing neighbors with a well-designed facility that can better control noise and odors.

Kent-Auburn conveyance system improvements (Phase A)

King County constructed two new pipelines, the Kent East Hill Diversion in Kent and the Stuck River Trunk in Auburn. These pipelines provide required capacity to accommodate recent and projected growth in Kent and Auburn.

Kent-Auburn conveyance system improvements (Phase B)

King County installed new sewer lines and replaced aging pipes in Pacific, Algona, and Auburn. Work also included modifications at the Pacific Pump Station.

Kirkland pump station and sewer upgrade

This project increased station pumping capacity, replaced aging equipment, and installed a larger diameter sewer force main to accommodate increased flows.

M Street trunk repair

King County has repaired a section of corroded pipe at the intersection of M Street NE and 2nd Street NE in Auburn.

Magnolia Wet Weather Storage Facility

The Magnolia Wet Weather Storage Facility at Smith Cove is designed to store excess flows of stormwater and sewage. The facility’s 1.5 million-gallon underground storage tank will help keep sewage and stormwater out of Puget Sound during storms.

Murray Wet Weather Facility

King County completed construction on an underground storage tank (Murray Wet Weather Facility) near the Murray Pump Station in West Seattle. The tank is designed to contain up to 1-million gallons of stormwater and wastewater during heavy rains, which will protect public health and the environment by controlling combined sewer overflows that occur near Lowman Beach Park

North Beach combined sewer overflow control

The wet weather storage facility is now operational. While the bulk of construction work was completed in December 2015, the contractor completed some work on the pump station site through early 2017. This included work on the new building, final landscaping and drainage improvements.

North Beach force main maintenance

To avoid premature replacement of usable assets, King County performs inspections and condition assessments throughout the life of wastewater pipelines. King County carried out a project to evaluate the condition of the North Beach Force Main, installed in 1963.

North Beach outfall assessment

A project team assessed the condition and looked at repair/replacement options for outfall #48a. This outfall is used to discharge combined sewer overflows (CSOs) from the pump station.

North Creek Interceptor

The County has completed repairs and replacement of a 2-mile pipeline that has been serving the Bothell area since 1970. The new pipeline will increase system reliability and capacity to accommodate population and business growth in this portion of the service area.

North Creek Storage Facility

Construction on the King County North Creek Storage Facility was completed Spring 2004. The 6-million-gallon underground storage facility manages excess wastewater and reduces overflows in Bothell, Kenmore and nearby communities north of Lake Washington.

Rainier Valley wet weather storage

King County has completed construction of a new combined sewer overflow (CSO) underground tank and sewer pipelines in Seattle’s North Beacon Hill and Columbia City neighborhoods, which control overflows of stormwater and sewage into the Duwamish River during heavy rains.

Ravenna Creek pipe extension

This project was completed in three phases from May 2008 to September 2011. During phase A, aggressive cleanup measures were implemented after an accidental wastewater release into University Slough. Phase B consisted of extending the pipeline that conveys Ravenna Creek downstream from Ravenna Park. Phase C involved the installation of three large logs with root wads in University Slough as mitigation for the temporary rerouting of Ravenna Creek flow to the combined sewer system.

Skyway infiltration and inflow reduction

This project replaced side sewers serving 332 residential properties; repaired or replaced public sewer mains and manholes; and disconnected improper storm drainage connections to the sanitary sewer.

Sunset and Heathfield pump stations upgrades

This project upgraded both pump stations, the connected force main pipe and the Eastgate Trunk structure near I-90.

Sweyolocken pump station

The updated Sweyolocken Pump Station, located next to Bellevue Way and the Mercer Slough Nature Park, handles increased flows.

West Point office annex

Construction was completed in August 2012 at the West Point Treatment Plant to build a permanent, modular office annex to replace temporary construction trailers. The new office space incorporates ‘green’ building materials and energy efficient design.

West Point Treatment Plant screenings improvement

This project addressed updated Washington State biosolids regulations to remove inert objects (trash and plastics) from solids destined for fertilizer use on farms and managed forests. King County installed new bar screens in the existing operating building and constructed a new building adjacent to the existing operating building to process the additional screened material.